So I tried to find the mathematical formula which guess the value of any object at a higher level. The result of this experiment, though disappointing, at least explains why since the release of the game, no one is started to provide an answer to this question.

The answer is simple. There is a different mathematical formula for each item. Also drawing the graph of a point table demonstrates that there might be more than one formula per item.

For now, as long as I would not have found a simple solution to this problem, I present the value of objects with known levels.
See Cooking and Recipes (RF2)

Known Levels of Items

Classification

Name

Level

2

3

4

5

6

7

8

9

10

Range

Mineral

Silver

220

275

330

440

550

660

770

880

990

1100

Mineral

Bronze

90

91

99

105

108

135

[90-135]

Mineral

Iron

80

84

88

96

100

104

120

[80-120]

Mineral

Scrap Iron

4

4

5

6

8

12

16

40

[4-40]

Mineral

Platinum

620

775

806

868

930

992

1054

1116

1178

1240

Mineral

Gold

430

516

559

645

Gems

Diamond

660

726

759

3300

[660-3300]

Gems

Ruby

250

750

1000

Gems

Aquamarine

170

255

765

Gems

Emerald

170

425

Gems

Sapphire

540

810

Gems

Amethyst

220

-

-

1

2

3

4

5

6

7

8

9

10

Range

Crystals

Wind Crystal

250

625

[250-725]

Crystals

Water Crystal

250

262

375

500

[250-725]

Crystals

Fire Crystal

250

625

[250-725]

Crystals

Magic Crystal

320

384

416

480

544

576

640

[320-640]

Crystals

Little Crystal

740

769

784

814

828

843

858

873

888

[740-888]

Crystals

Earth Crystal

250

725

[250-725]

Cloth & Skin

Large Fleece

600

624

Cloth & Skin

Medium Fleece

400

416

Cloth & Skin

Small Fleece

200

208

Cloth & Skin

Small Yarn Ball

480

499

Cloth & Skin

Medium Yarn Ball

680

707

Cloth & Skin

Large Yarn Ball

880

915

-

-

1

2

3

4

5

6

7

8

9

10

Range

Stick & Stem

Root

135

137

143

148

155

162

168

175

189

202

Stick & Stem

Sparkle String

110

112

116

121

126

131

137

142

147

153

Stick & Stem

Strong Vine

65

78

Stick & Stem

Strong String

80

96

104

112

120

128

136

144

[80-150]

Stick & Stem

Plant Stem

50

51

53

55

57

65

70

[50-80]

Stick & Stem

Branch

15

Stick & Stem

Wood

5

Powder & Liquid

Devil Blood

540

581

591

[550-620]

Powder & Liquid

Fairy Dust

650

689

728

741

754

[650-800]

Powder & Liquid

Glue

80

83

84

86

91

92

96

[80-96]

Powder & Liquid

Poison Powder

40

46

Powder & Liquid

Magic Powder

480

499

508

518

258

537

547

566

[508-600]

Powder & Liquid

Gunpowder

Powder & Liquid

Spore

140

145

148

151

154

165

[140-180]

-

-

1

2

3

4

5

6

7

8

9

10

Range

Chunk

Speckled Skin

70

71

74

77

80

84

91

98

[70-110]

Chunk

Insect Jaw

410

426

434

442

451

459

467

483

[426-525]

Chunk

Insect Skin

70

73

77

84

105

210

[70-210]

Chunk

Scorpion Tail

120

122

127

132

144

156

180

[120-180]

Chunk

Scorpion Pincer

168

174

178

181

191

198

201

[168-201]

Shards

Broken Box&Glue

79

82

83

85

90

91

95

[79-95]

Shards

Broken Hilt

58

Cloth & Skin

Quality Cloth

50

60

67

75

82

90

97

105

125

[50-125]

Cloth & Skin

Cheap Cloth&Bandage

30

31

33

34

36

45

60

90

120

150

[30-150]

Shards

Shoulder Piece

55

57

60

66

71

82

110

137

[55-155]

Cloth & Skin

Hood

540

561

572

583

594

604

615

626

648

[540-648]

Shards

Arrowhead

25

37

50

110

120

[25-130]

Cloth & Skin

Silk Cloth

500

530

120

Cloth & Skin

Cheap Cloth&Bandage

30

31

33

34

36

45

60

90

120

150

[30-150]

Shards

Giant's Gloves

280

291

296

302

308

313

319

336

[280-336]

Shards

Hammer Piece

550

572

583

594

605

616

627

638

[550-700]

Cloth & Skin

Wooly Furball

60

61

63

66

69

90

[60-90]

Chunk

Can

1

Chunk

Boot

1

-

-

1

2

3

4

5

6

7

8

9

10

Range

Claws & Bones

Rage Fang

690

717

731

745

759

772

800

[690-890]

Claws & Bones

Wolf Fang

130

136

149

260

390

650

[130-650]

Claws & Bones

Bird Wing

55

66

74

82

90

99

107

129

[55-140]

Claws & Bones

Skull

40

44

50

80

240

400

[40-400]

Cloth & Skin

Quality Fur

360

374

388

396

[360-500]

Claws & Bones

Tortoise Shell

180

189

198

270

[180-580]

Claws & Bones

Hard Horn

150

180

202

315

352

375

[150-375]

Claws & Bones

Devi Horn

770

800

831

847

[770-970]

Claws & Bones

Giant's Fingernail

240

249

254

264

268

278

288

[240-288]

Claws & Bones

Panther Claw

90

112

135

405

[90-450]

Claws & Bones

Bull Horn

410

426

434

442

459

467

[410-550]

Cloth & Skin

Fur

220

233

237

255

264

[220-264]

Claws & Bones

Fish Fossil

120

124

127

129

132

136

141

144

[120-144]

Misc

Proof of Warrior

50

52

55

57

60

100

150

250

[50-250]

Chunk

Rock

2

Apple

60

63

66

74

78

90

120

150

[60-200]

Other Tables

If someone have something to add, don't hesitate to post comment or to edit this page.